This invention relates to the field of centrifuge rotors and, more particularly, relates to a process for making a one piece rotor liner having a convolute configuration defining separate chambers which are automatically sealed and unsealed from each other during certain phases of the centrifugation operation.
In the recent development of air driven ultra high speed centrifuges, a new rotor liner configuration has been developed which establishes at least two separate and distinct chambers within the rotor that are in fluid communication with each other during the high speed centrifugation operation, but assume sealing engagement from each other subsequent to centrifugation to isolate specific centrifugated constituents of the sample mixture and to avoid remixing. Reference is made to a U.S. Pat. No. (4,056,225) issued to George N. Hein, Jr. entitled A Centrifuge for Separating Phases of a Liquid Ser. No. 681,312, filed Apr. 29, 1976 and a patent to George N. Hein U.S. Pat. No. (3,096,283) entitled a Container for Blood and Machine for Separating Precipitates from Liquid Blood Constituents. Present construction methods for making the above-referenced rotor liner requires the use of two separate pieces to obtain the tight convoluted configuration, necessitating a bonded seal between the respective pieces. The generally enclosed rotor liner has a somewhat cylindrical configuration and the presently used bonding between the two sections of the liner is normally placed along a junction located at the outer circumferential extremity of the annular chamber.
The bonded joint between the respective sections of the liner establishes a potential weak point in the liner which could be subjected to leakage or rupturing under certain conditions. It is extremely difficult to develop a dependable and reliable bonded joint which can withstand the high hydrostatic pressures of the centrifugation operation. Since the bonded joint is located at the outer diameter of the annular chamber, it is exposed to the greatest forces from the centrifugation induced pressure of fluid mixture within the annular chamber. Also, because the rotor must be in perfect balance, the presence of a bonded joint poses a potential contributing factor to possible imbalance of the rotor. Typically a small mating flange is formed on each of the pieces to accommodate the bonding process, causing an undesirable increase in the outer diameter of the annular chamber.
The necessary convolute configuration within the generally enclosed liner that establishes the separating wall between the inner chamber and the annular chamber has dictated the presently used two piece configuration. The separating wall has its upper edge in proximity with the top section of the liner, presenting a narrow annular flow path between the inner chamber and the annular chamber. The rotor liner, having only a small access hole in its top section, is not capable of being made by an injection molding process to establish a single one piece rotor liner, because it would be impossible to remove a mandrel with the rather unique convoluted configuration after forming the liner. Therefore, the liner has been designed for fabrication in two pieces with the top section being bonded to the lower section.
The interior volume of both the annular and inner chambers with respect to each other and with respect to the size of sample fluid mixture used in the centrifugation must be closely controlled. In the case of a blood sample, centrifugation is used to separate out a clear serum from the chyle and other constituents. Further, there must be enough clear serum obtained to perform the desired diagnostic tests. Otherwise, further blood samples from the patient would be required. If, for instance, the inner chamber were too small, some chyle might accumulate in the annular chamber with the clear serum. If the annular chamber were too small, not enough serum would be available for conducting the diagnostic tests. In addition, if the chambers were made too large, there may not be the proper cross flow between the chambers during centrifugation. Consequently, the respective volumes of the chambers is quite critical and it has always been considered a necessity to use the two piece construction to precisely obtain the desired volumes.